# prestack migration

Post on 05-Feb-2016

66 views

Category:

## Documents

Embed Size (px)

DESCRIPTION

Prestack Migration. Intuitive. Least Squares. Green’s Theorem. Migration. 3D Prestack Diffraction Stack Migration. Motivation: ZO only good if no lateral vel change. s. g. x. . =. d(x’ ,  +  ). x g. s x. s, g. 3D Prestack Diffraction Stack Migration. - PowerPoint PPT Presentation

TRANSCRIPT

• Prestack MigrationMigration

• 3D Prestack Diffraction Stack MigrationgsxMotivation: ZO only good if no lateral vel change

• Trial image pt xm(x) = 3D Prestack Diffraction Stack Migrationgsx

• OutlinePrestack DS Migration TheoryRTMMATLAB CodeRTM vs Poststack vs Prestack

• Prestack MigrationQuestion: Why Prestack when poststack migration seems good enough?Answer: Stacking to get stacked section assumes layered medium assumption.Solution: Migrate shot gathers so no layer assumption needed. This is prestack migration.

• Narrow band case: direct wave correlated with dataDiffraction Stack Migration: PrestackWhere is scatterer?Down timeUp time

• A(s,x)sxiexgieA(g,x)d(s,g) =115.Diffraction Stack Modeling: Prestack~d = L m

• A(s,x)sxiexgieA(g,x)m(x) =d(s,g)~*--Narrow band case: direct wave correlated with data..115.Diffraction Stack Migration: Prestack~m(x)

• OutlinePrestack DS Migration TheoryRTMMATLAB CodeRTM vs Poststack vs Prestack

• Prestack RTM vs One-way Wave Equation Migration

• Prestack RTM vs One-way Wave Equation Migration

• Trial image pt xZO Diffraction Stack Migration

• Trial image pt xMigration ImageZO Diffraction Stack Migration2D dot product of migration Operator and d(g,t)

• Trial image pt xZO Reverse Time Migration

• Trial image pt xZO Reverse Time Migration

• Prestack RTM vs One-way Wave Equation Migration

• OutlinePrestack DS Migration TheoryRTMMATLAB CodeRTM vs Poststack vs Prestack

• Types of TraveltimesShortest Traveltime or Shortest Raypath Maximum Energy Traveltimes

• Poststack vs Prestack Migration

• Poststack vs Prestack Migration

• RRTM vs KM Migration

• RRTM vs KM Migration

• Prestack RTM vs One-Way Mig.

• Prestack RTM vs One-Way Mig.

• OutlinePrestack DS Migration TheoryRTMDS MATLAB CodeRTM vs Poststack vs Prestack

• MATLAB Prestack Migration

• MATLAB Inefficient Prestack Migrationfor isx=1:nx % Loop over shot for igx=1:nx % Loop over receivers for ix=1:nx % Loop over model x for iz=1:nx % Loop over model z t=timer(ix,iz,isx)+timer(ix,iz,igx) sample=gather(isx,igx,t) % Shot gather has 2 time derivatives mig(ix,iz)=mig(ix,iz)+sample end end endend

• MATLAB Prestack Migration

• Prestack Migration1. No assumption about velocity model2. More sensitive to velocity model errors compared to poststack migration3. More than 10 10 times slower than poststack migration4. More sensitive to velocity model than time migration26

• Poststack vs Prestack Migration

• Poststack vs Prestack Migration

• ZO Reverse Time Migration

• Is Superresolution by RTM Achievable?Tucson, Arizona Test60 mThis is highest fruit on the tree..whom dare pick it?(Hanafy et al., 2008)

• Is Superresolution by RTM Achievable?Tucson, Arizona Test60 mThis is highest fruit on the tree..whom dare pick it?(Hanafy et al., 2008, TLE)